Apparatus for holding liquefied gases



Oct. 31, 1967 L. c. BROWNING ETAL 3,

I APPARATUS FOR HOLDING LIQUEFIED GASES 2 Sheets-Sheet 1 Original Filed June 29, 1959 L. c. BROWNING ETAL 3,350,105

APPARATUS FOR HOLDING LIQUEFIED GASES Oct. 31, 1967 2 Sheets-Sheet 2 Original Filed June 29, 1959 mk b . lxmy Z7 74 Q. m $1M United States Patent APPARATUS FOR HOLDING LIQUEFIED GASES Lester C. Browning, deceased, late of Norristown, Pa., by Ruth C. Browning, executrix, Norristown, Pa., and David A. Williams, Livermore, Calif assignors to Chemetron Corporation, Chicago, Ill., a corporation, of Delaware Application May 1, 1963, Ser. No. 283,130, now Patent No. 3,251,602, dated May 17, 1966, which is a division of a plication Ser. No. 823,400, June 29, 1959, now Patent No. 3,109,293, dated Nov. 5, 1963. Divided and this application Oct. 18, 1965, Ser. No. 497,492

1 Claim. (Cl. 277--26) This is a division of copending United States patent application Ser. No. 283,130, filed May 1, 1963, now Patent No. 3,251,602, which is a division of United States patent application Ser. No. 823,400, filed June 29, 1959, now Patent No. 3,109,293.

It is an object of the present invention to provide a novel dam ring assembly for isolating the liquid sump from the gas chamber.

Another object of the present invention is to provide for the warm end of the pump a new and improved low pressure seal which is of simple construction but is, nevertheless, effective to prevent the escape of cool gas through the warm end and, at the same time, to isolate the packings at the warm end of the pump from the cool liquefied gases, thereby preventing these liquefied gases from adversely affecting the packings.

A further object of the invention is to provide a new and improved arragement for isolating the cold liquid sump from the warm end of the pump when the pump is shut down.

The foregoing and other objects are realized, sealing means in the form of a damringis interposed between the pump body and the fixed structure to isolate the gas chamber from the liquid reservoir. To equalize the pressures on opposite sides of the dam ring, the liquid reservoir is connected to the gas chamber through means including a small bleed line leading to the gas chamber through the mounting flange. This bleed line includes a check valve which is operated automatically in response to an increase in pressure in the gas chamber caused, for example, by inadvertant flow of liquefied gas into this chamber and the subsequent volatilization of this liquefied gas. The check valve prevents further flow of fluid to the chamber until the high pressure subsides.

The invention, both as to its organization and manner of operation, together with further objects and advantages thereof, will best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is an elevational view partly broken away showing a high pressure pump comprising the present invention;

FIG. 2 is an enlarged, sectional view of a portion of the right end of the pump shown in FIG. 1;

FIG. 3 is an enlarged, sectional view of the dam ring employed on the pump shown in FIG. 1;

FIG. 4 is an enlarged, sectional view showing an alternative construction of the dam ring;

FIG. 5 is an enlarged, sectional view showing still another modification of the darn ring; and

FIG. 6 is an enlarged, sectional view showing a further modification of the dam ring.

Considering now a high pressure pump and referring first to FIG. 1 of the drawings, the pump of the present invention is there illustrated as comprising a pump body or casing 60. A shell (not entirely shown) includes a housing 61 cooperating with the pump body to define a gas chamber 62 and a liquid sump or reservoir 63. To this end, the housing 61 includes a cylindrical sleeve 64 and a somewhat cup-shaped cover joined together by an annular support ring 66. The cup-shaped cover opens to a fluid line (not shown) in order to permit the flow of fluid from a tank to the liquid sump 63.

To attach the pump body to a shell portion 23 of a tank (not shown), this body is provided with a radially and outwardly extending mounting flange 67 secured to the shell 23 by means of a plurality of mounting screws 68. The pump body includes a cylinder portion or annular member 69 extending within the housing 61 and through the chambers 62 and 63 so that the pumping or cold end of the pump is immersed within the body of the liquefied gas. The pumping elements are, therefore, maintained at the proper operating temperature and the pump can be started without priming. The cylinder portion 69 is spaced from the sleeve 64 and from the cover 65 to define the chambers 62 and 63 referred to above. A novel dam ring assembly 70, which will be described more fully hereinafter, cooperates with the annular ring support 66 and with the cylinder portion or annular member 69 to isolate the gas chamber 62 from the liquid sump or reservoir 63. The gas chamber is relatively long and serves to inhibit the transfer of heat from the mounting flange to the liquid in the sump '63 and also to isolate the packings at the warm end of the pump from the cold liquefied gases. It should be observed that heat can be transferred from the warm end of the pump to the cold end not only by the metal contact but also by conduction, convection and radiation through the gas in the chamber 62. To avoid the transfer of heat through the chamber 62 and to isolate the mounting flange from the cold portion of the pump, the chamber 62 is preferably packed with a wadded, crumpled, highly reflecting, metal foil such as aluminum as is indicated by the reference numeral 59. Due to the reflectivity of the foil, radiation through the chamber 62 is reduced. Since the volume of the chamber is substantially filled with foil, there is little gas circulation and, hence, very little heat is transferred by convection. Since the foil is wadded and crumpled, it provides a large number of very long heat paths thus reducing the heat transfer due to conduction.

The pump body 60 also includes a cage or super structure 72 suitably secured to the mounting flange 67 and extending outwardly from the shell 23 to be exposed to the ambient. For ease of manufacture, the cylinder portion 69 is preferably formed by a plurality of separate pieces including a central sleeve 73 and a head 74 suitably secured to the sleeve by means of a plurality of spaced apart cap screws 75. A reciprocating piston or annular member 77 mounted for sliding movement longitudinally of the cylinder 69 effects the pumping action by drawing fluid from the sump 63 into the cylinder 69 during its suction stroke and by delivering pressurized fluid from the cylinder during its pressure stroke. Simple, automatically operated valves constructed as described below control the flow of fluid into and out of the cylinder 69.

To reciprocate the piston, the latter is connected through a ball and socket assembly 78 to a connecting rod 79 which is reciprocably driven by any suitable mechanism of conventional construction. The connecting rod 79 is connected by means of a Wrist pin 80 to a cross head 81. The cross head includes an axially extending recess 82 for accommodating the head of the connecting rod 79 together with a pair of diametrically opposed openings for respectively receiving the ends of the wrist pin 80 which also extends through the recess 82 and through a transverse opening in the head of the connecting rod. The cross head is also provided with an annular, peripheral recess 83 cooperating with the main body of the cross head to form a shoulder 84 against which is seated a bushing 85. The latter bushing is retained in position by means of a lock nut 86 threaded onto the cross head 81. When the connecting rod 79 is reciprocated, the bushing slides within a cylindrical sleeve 87 suitably supported from the super structure 72. The reciprocating movement of the connecting rod 79 is transmitted through the ball and socket assembly 78 to the piston rod 77 with the result that the latter rod is moved back and forth within the cylinder head 69.

During the suction stroke of the piston 77, liquid is drawn from the sump 63 through the head 74 of the cylinder and into an inlet chamber 99. This fluid passes through -a filter screen 100 which removes any foreign particles or debris. The fluid from the filtering screen is delivered to a plurality of spaced apart openings 101 extending parallel to each other through the head 74. Fluid flow through each of these openings 101 is controlled by means of an inlet valve ball 102. All of the valve balls 102 are mounted upon an annular supporting cage 103 secured to the head 74 by means of a plurality of spaced apart socket headed cap screws (not shown).

Each of the valve balls 102 is guided for movement upon the cage 103 by means of a pair of parallel slots 102a and 102b respectively formed in the two sides of the cage. The ball has a diameter which is greater than the width of the slots and is also greater than the spacing between the sides whereby the movement of the ball is restricted to a path extending axially of its associated opening 101. The cage 103 is dimensioned to accommodate an axially extending projection 77a formed on the piston rod 77 when the latter rod is advanced or extended at the completion of its pressure stroke. The reduced pressure created in the inlet chamber 99 during the suction stroke of the piston rod allows the valve balls 102 to be unseated by pressure external to the pump so that fluid from the sump 63 passes through the openings 101 and into the inlet chamber 99. The fluid flow past each valve ball is uniform on both sides of the ball since the fluid passes along the ball through the slots 102a and 102b. Thus, the valve balls do not spin or turn when the fluid is drawn into the inlet chamber and, as a consequence, these balls are not subjected to excessive wear. Moreover, fluid passing through the valves is not forced to undergo an abrupt or sharp turn, a feature which avoids turbulence and prevents cavitation of the pump on the suction stroke.

When the piston moves to the right as viewed in FIG. 1, that is, during its advance or pressure stroke, the pressure created within the chamber 99 seats the valve balls 102 to close the openings 101 and, hence, to prevent the escape of fluid from the inlet chamber to the liquid sump 63. Fluid under pressure then flows from the inlet chamber through an outlet passage formed in the cylinder 69. This outlet passage includes a radially extending opening 107 communicating with an elongated passage 108 extending longitudinally of the cylinder 69. A spring biased discharge valve 109 is inserted within the elongated passage 108 to control the flow of outlet liquid. This discharge valve includes a valve ball 110 biased by means of a coil spring 111 towards an annular valve seat defined by a shoulder 112 in the passage 108. The spring 111 acts against a plug 113 which includes a central body portion 113a and a plurality of outwardly extending fins or ribs (not shown). These fins are received within the chamber 114 for the outlet valve and define a plurality of guide slots (not shown). The coil spring 111 biases the ball 110 towards one end of the chamber 114. The slots also accommodate the ball 110 to guide the latter as it is moved towards and away from the valve seat shoulder 112. When the ball is unseated, fluid flows uniformly around all sides of the valve ball and through the four slots so that this ball is not spun or turned by the moving liquid. It will be observed that the liquid flowing past the valve is not forced to make a turn in direction as it passes therethrough and, hence, the beneficial results described previously are realized.

In view of the foregoing description, it will be observed that during the pressure stroke of the piston rod 77 the pressure of the fluid in the chamber 99 becomes sufiicient to overcome the action of the biasing spring 111, thus unseating the valve ball 110 and delivering fluid to the outlet passage 108. The fluid in the passage 108 passes through the central sleeve 73 and is delivered to an L- shaped passage 116 formed in an end sleeve or annular member 117 forming part of the cylinder 69. The L- shaped passage 116 opens to a fitting or coupling 118 which is connected to a tube 119 extending through the gas chamber 62. The tube 119 is, in turn, connected through a sleeve coupling 120 mounted upon the flange 67, to a tube 121 and a fitting 122 in order to deliver fluid to an outlet line 50. The relatively cold liquid flowing through the tube 119 does not cool the packings around the flange 67 due to the insulation provided by the gas chamber 62 and by the packing 59 previously described.

In accordance with an important feature of the present invention, the central sleeve 73 of the cylinder 69 is lined by a cylindrical wear sleeve or liner 125 which is formed of a suitable hardened metal such as chrome iron in order to resist wear caused by reciprocation of the piston rod. The length of the sleeve 125 may be varied as required but it is preferably somewhat longer than the stroke of the piston. The wear sleeve 125 is provided with an annular flange 126 at one end thereof seated within a suitable recess defined adjacent one end of the central sleeve 73. The wear sleeve is dimensioned so that at ambient temperatures its outer diameter is slightly smaller than the inner diameter of the central sleeve 73 and, as a result, during assembly of the pump, it can be inserted very easily into the interior of the sleeve 73 whereupon the head 74 can be attached to complete the assembly. The cylinder 69 and, more particularly, the central sleeve 73 is formed of a suitable metal, such as bronze, which has a much higher coefiicient of contraction than the material of the wear sleeve 125 and, as a result, the differential contraction between the sleeve 73 and the wear sleeve 125 causes the wear sleeve to be tightly retained within the cylinder when the pump reaches cryogenic temperature. The tight fit between the wear sleeve and the pump body is not disturbed by vibration of the pump and, hence, the wear sleeve does not turn or vibrate when the piston rod is reciprocated. Since the pump body is made of bronze it possesses suflicient elasticity to avoid rupture of the sleeve when the parts contract.

The piston rod 77 may be spaced somewhat from the inner surface of the wear sleeve 125 and, hence, these parts need not be machined within strict tolerances, thus providing a construction which can be manufactured very easily and inexpensively. By avoiding the necessity for a tight fit between the piston and the wear sleeve, the heat generated by friction is reduced and excessive volatilization of the liquefied gas is prevented. The spacing between the wear sleeve 125 and the piston rod forms a gas pocket which is indicated in FIG. 2 by the reference numeral 128. This gas pocket is sealed from the inlet chamber 99 by means of a plurality of sealing assemblies 130, 131, 132, etc. The number of such assemblies employed may vary but a suflicient number is used to provide the desired sealing action. These sealing assemblies are substantially identical in construction and, hence, only one will be described in detail, namely, the assembly 132. This assembly includes an annular filler member 133 having an external recess 134 therein for receiving a sealing ring 136 and an expander ring 137. The filler member is seated against the piston rod 77 and is retained in alignment with the other sealing assemblies by means of a lock nut 138 forming part of the piston rod 77. The lock nut 138 is threaded onto the end of the rod and compresses the line of sealing ring assemblies against a shoulder 139 formed on the piston rod. The expander ring 137 is a split, resilient ring which acts to bias the sealing ring 136 into engagement with the inner wall of the wear sleeve 125. This expander ring is preferably formed of a material such as beryllium copper having a width dimension approximately equal to the width of the sealing ring 136 for the purpose which will be evident as the description proceeds. The sealing ring is formed of a plastic material which at cryogenic temperatures becomes very hard and resistant to wear but which, at temperatures near the ambient temperatures of the pump, exhibits plastic flow to form a good seal with the inner surface of the cylindrical wear sleeve 125. In addition, the material of the ring must be one which is not hazardous in the presence of the liquified gas being pumped. In accordance with an important feature of the present inventi-on, the sealing ring 136 is formed of a fluorinated hydrocarbon such as polymonochlorotrifluoroethylene (a material sold under the trademark Kel-F by M. W. Kellogg Company) or polytetrafluoroethylene (a material sold under the trade name Teflon by E. I. du Pont & Company). The sealing ring 136 is split and its two ends are cut away. The cutaway portions are overlapped to provide a fairly good sealand, in addition, the expander ring 137 underlies the overlapped joint to prevent the escape of liquefied gas through this joint. Since the width of the expander ring 137 is approximately equal to that of the sealing ring 136, the entire joint is covered. Moreover, the split in the expander ring 137 is diametrically opposed from the split in the sealing ring, thus blocking the flow radially through the joint. In addition, in order to avoid a straight line path for the flow of liquefied gas from the chamber 99 to the gas pocket 128, the splits in the sealing rings of the various assemblies 130, 131 and 132 are displaced or misaligned with respect to each other. Thus, the split of the assembly 130 is displaced 120 degrees from the corresponding splits in each of the assemblies 131 and 132 while the split in the assembly 131 is displaced 120 degrees from the corresponding splits in both of the assemblies 130 and 132 and so on.

In assembling the pump shown in FIG. 1, the sealing ring 136 forms an efiective seal against the wear sleeve 125 at the ambient temperature of the pump and when the pump temperature is reduced the sealing ring hardens and becomes highly resistant to wear. After use of the pump, the sealing ring 136 of each assembly may wear and, hence, in accordance with an important feature of the present invention, each sealing ring is resealed after a predetermined period of operation. It has been found that the pump will run for approximately 1500 hours before requiring reseal of the rings 136 and, hence, at the end of this period, the pump is shut down and the rings are permitted to reach ambient temperature whereupon they reseal themselves by the plastic flow referred to above. After the reseal operation is completed, the pump can be operated for another 1500 hours before the rings must be resealed again. The useful life of a set of rings can thus be extended to a period in excess of 10,000 hours whereas in pumps of prior design, replacement of these rings every few hours of operation was necessary. The expander ring 137 exerts sufiicient pressure on the sealing ring 136 to accomplish the plastic flow at the ambient temperatures but this pressure is insufii-cient to cause excessive wear on the rings during operation at cryogenic temperatures.

A vent line including manually operated valve (not shown) referred to above is connected from the gas pocket 128 to the upper end of the tank. This connection is made through a collecting ring 140 positioned adjacent the end of the end sleeve 117. The collecting ring 140 includes an inner annular recess 140a extending around the collecting ring adjacent the periphery of the piston rod 77 and an outer annular recess 14011 concentric with the recess 140a and disposed adjacent the connecting sleeve 117. The annular recesses 140a and 14% are interconnected by a plurality of spaced apart apertures or openings 1400 which permit the flow of gas from the pocket 128 to an opening (not shown) in sleeve 117. The opening is connected through a tube 142, through a connector 143 carried by the mounting flange 76 and through a suitable connecting line 144. When the pump is operating, a valve (not shown) is opened to vent the gas pocket 128 to the tank. It will be understood that gas may be created within the pocket 128 by vaporization of small amounts of leakage liquefied gas which may enter the pocket around the sealing ring assemblies. The venting of the gas, of course, prevents vapor binding of the pump at low suction heads.

When the pump is shut down, the valve (not shown) is closed with the result that liquid trapped in the pocket 128 will be vaporized due to heat infiltration from the mounting flange 67. The evolved gases create a pressure in the gas pocket 128 which forces the liquid back into the inlet chamber 99 thus isolating the liquefied gas from the mounting flange, increasing the heat leakage path and, hence, reducing the vaporization of the liquid when the pump is not running. The operation of the valve to force the liquid back into the inlet chamber 99 is a particularly desirable feature when the pump is continuously immersed, that is, when the inlet chamber is continuously filled with liquefied gas from the sump 63.

Considering next the construction of the dam ring assembly 70 and referring particularly to FIGS. 2 and 3 of the drawings, it will be observed that this assembly comprises an annular cup-like sealing member 150 encircling the cylinder 69 and seated against the annular support ring 66. To this end, the member 150 includes, in the form shown in FIGS. 2 and 3, an outwardly extending flange 151 for engaging the side edge of the support ring 66 together with a pair of laterally extending lips 152 and 153 formed by an annular groove 154 in its side face. The outer lip 152 is seated against the inner edge of the ring 66 while the inner lip engages and seats against the periphery of the cylinder 69. The member 150 is urged axially of the cylinder and into engagement with the support ring 66 by means of a pressure exerting back-up assembly 165 which functions to prevent the member 150 from being displaced as a result of pressure differences on opposite sides of the dam ring 70. The assembly 165 includes a plurality of spaced apart biasing springs 155 acting against an annular collar 156 mounted for sliding movement upon the cylinder 69. Each of the springs 155 encircles a guide rode 157 which has one end secured to the collar 156 and has its other end extending through a guide slot or aperture formed in a fixed collar 158 secured to the cylinder 69. The ends of the guide rods may be connected together by means of a connecting Wire 159 to provide for uniform expansion or contraction of the springs and, hence, to exert uniformly distributed pressure upon the sliding collar 156. The springs 155 obviously urge the collar 156 toward the right as viewed in FIG. 2 so that this collar acts upon the member 150 to seat the flange 151 against the annular ring 66.

The member 150 is preferably formed of a suitable material such as polytetrafluoroethylene (Teflon) which has a coeflicient of contraction somewhat higher than that of the bronze metal forming the central sleeve 73. The member 150 is dimensioned so that at ambient temperatures, it will readily slide onto the cylinder 69 but when the temperature of the pump is reduced to the cryogenic range, the Teflon member 150 contracts more rapidly than the cylinder 69, thus forming a tight seal between the inner lip 153 and the outer periphery of the cylinder. For the purpose of providing a similar seal between the outer lip 152 and the inner edge of the annular support ring 66, a seating ring 160 is disposed within the groove 154. This seating ring is preferably formed of a suitable metal such as Invar which has a coefiicient of contraction considerably lower than that of the metallic support ring 66. Thus, while the member 150 can be readily inserted into the support ring 66 at ambient temperatures, when the pump reaches cryogenic temperatures the support ring 66 contracts much more than the seating ring 160 with the result that the outer lip 152 is clamped between these two members to form a liquid tight seal.

The lower edge of the member 150 adjacent the inner lip 153 is relieved as indicated at 161 by providing an outwardly tapering portion facing the cylinder 69 but extending away from this cylinder. This relieved portion permits distortion of the inner lip 153 radially with respect to the outer lip 152 without distorting the outer lip and thus avoids breaking the seal between the lip 152 and the annular ring 66. In addition, this relief allows the member 150 to absorb the vibrations of the high pressure pump without destroying the seal at the outer lip 152.

In order to prevent the existence of large differential pressure existing in the chamber 62 and 63 on opposite sides of the assembly 70, means are provided for connecting the gas chamber 62 to the chamber 63 through the upper portion of the tank. More specifically, the liquid sump or reservoir 63 is connected through a small bleed line (not shown) to the upper end of the tank. In addition, the gas chamber 62 is connected through a fitting 165 and through a check valve 57 (not shown) referred to previously to the upper end of the tank. The bleed line connection between the gas chamber 62 and the liquid sump 63 thus equalizes the pressure on opposite sides of the assembly 70 and prevents a large pressure differential thereacross which might otherwise result in rupture of the seal between the ring 66 and the member 150. Liquefied gas inadvertently conducted'to the gas chamber 62 is volatilized by the heat to develop a gas pressure for automatically closing a check valve (not shown) in order to prevent the further flow of liquefied gas to the chamber 62.

An alternative construction of the darn ring assembly and its associated parts is illustrated in FIG. 4. This construction is somewhat similar to that shown in FIG. 3 and, hence, corresponding parts have been assigned the same reference numerals except that in the construction shown in FIG. 4, the reference numerals are in the 200 series. Thus, for example, the cup-like member has been assigned reference numeral 250, the annular groove therein has been assigned reference numeral 254, the outer lip bears the reference numeral 252, the inner lip bears the reference numeral 253, the outer flange bears the reference numeral 251, the relieved portion bears the reference numeral 261, and so on. The main difference between the construction shown in FIG. 4 and that shown in FIG. 3 resides in the provision of an additional seating or clamping ring 262 disposed within the annular groove 254 and encircling the inner lip 253. This ring is formed of a material such as aluminum having a higher coefiicient of contraction than the cylinder 69 and, as a result, the ring 262 contracts much more than the cylinder when the pump reaches cryogenic temperatures. The contraction of the ring 262, of course, intensifies the seat between the inner lip 253 and the pump body 69 and, hence, prevents failure of this seal as might be caused, for example, by misalignment of the pump body-and the annular support ring 66.

A still further modification of the dam ring assembly is illustrated in FIG. 5 wherein the parts corresponding to those of the previous embodiments have been assigned reference numerals in the 300 series. Thus, the cup-like member is indicated by reference numeral 350, the outer lip bears reference numeral 352, the inner lip has been assigned reference numeral 353, the annular groove has been assigned reference numeral 354, the relieved portion is indicated at 361, and the annular support ring bears the reference numeral 366. The latter support ring is identical to the ring previously described except that its inner edge is provided with a tapered portion 366a which cooperates with a correspondingly tapered portion 360a on the ring 360 to form the outer seal. The ring 360 is so dimensioned that at ambient temperatures it fits readily into the ring 366 with the surface 360a and 366a contiguous to each other. The ring 360 is again formed of a material such as Invar having a lower coefiicient of contraction than the metal forming the annular support ring 366 and, as a result, the surfaces 360a and 366a are forced into firm engagement when the temperature of the pump reaches the cryogenic range. The outer lip 352 in the arrangement shown in FIG. 5 seats against the ring 360 and this lip is encircled by a seating ring 363 formed of a suitable metal such as aluminum having a much higher coefficient of contraction than that of the ring 360. Thus, when the operating temperature of the pump reaches the cryogenic range, the ring 363 clamps the outer lip 352 against the ring 360 to complete the outer seal. The tapered surface 360a on the ring 360 forms an extremely tight fit with the outer lip 352 when the aluminum 363 is contracted. Due to this tapered surface, it will be very difficult, if not impossible, to pull the outer lip 352 axially toward the left as viewed in FIG. 5 and, hence, the outer seal is not likely to be broken even though a slight difference of pressure exists between the gas'chamber 62 and the liquid sump 63. It has been found that a taper of two and one-half (2.5) degrees on the surface 360a and on the surface 366a provides particularly efficient holding action at the outer seal. A second ring 362 similar in construction to the ring 262 previously described may again be empolyed around the inner lip 353 to intensify the inner seal between the lip 353 and the cylinder 69.

A still further modification of the darn ring assembly is illustrated in FIG. 6 wherein the component parts corresponding to those of the modifications previously described have been assigned reference numerals in the 400 series. Thus, the cup-like member bears reference numeral 450, the outer lip is designated by reference numeral 452, the inner lip bears reference numeral 453, the relieved portion is indicated at 461, the annular support ring bears the reference numeral 466, the annular groove in the member 450 bears the reference numeral 454, and so on. The support ring 466 is similar to the ring 66 previously described but, in addition, it is provided with an annular groove 466b in one of its sides for receiving the outer lip 452. A metal seating ring 463 formed of aluminum or other material having a coefficient of contraction much higher than that of the material forming the support ring 466 is seated within the groove 4661) and encircles the outer lip 452. Thus, when the temperature of the pump reaches the cryogenic range, the ring 463 contracts more rapidly than the ring 466 in order to clamp the outer lip 452 against the inner wall of the groove 466b, thus forming a tight outer seal. Here again, a metal seating ring 462 similar to the ring 262 previously described is employed to intensify the seal between the inner lip 453 and the pump body 69.

Other embodiments and modifications of this invention will suggest themselves to those skilled in the art, and all such of these as come within the spirit of this invention are included within its scope as best defined by the appended claim.

What is claimed is:

In a pump for liquefied gases at cryogenic temperatures: a first annular member and a second annular member spaced outwardly from said first annular member, means providing a seal for liquefied gas between said first and second annular members including first ring means having a lesser coefficient of contraction then said second annular member, said first ring means being in sealing contact with said second annular member, said first ring means extending beyond said second annular member, a sealing ring having a portion overlying in contacting relationship said first ring means, said sealing ring having another portion overlying in contacting relationship said first annular member, and second ring means encircling said other portion of said sealing ring and having a higher coefiicient of contraction than said first annular member.

References Cited UNITED STATES PATENTS 674,325 5/ 1901 Walker 277-142 2,867,458 1/1959 Kroekel 277-142 X 2,927,830 3/1960 10 5/1960 Santapa' 277-26 1/ 1962 Fulton et a1 277-26 9/1963 Kerlin 277-206 6/ 1965 Skinner 277-205 X FOREIGN PATENTS 1908 Great Britain.

LAVERNE D. GEIGER, Primary Examiner.

Workman 277-205 X 10 J. S. MEDNICK, Assistant Examiner. 

